How to connect to a database using JDBC

Connecting to a database using JDBC (Java Database Connectivity) involves a few basic steps. Here are the main steps to create a JDBC connection.

Load the JDBC Driver

Make sure that the appropriate JDBC driver for the database you are using is in your project's classpath. You can do this by including the driver JAR in your project or using a dependency management tool like Maven or Gradle. The specific line to load the driver varies based on the database.

// example for MySQL
Class.forName("com.mysql.cj.jdbc.Driver");

Establish a Connection to the Database

Use the "Connection" class to establish a connection to the database. You will need to provide the database URL, username and password.

String url = "jdbc:mysql://localhost:3306/yourDatabase";
String user = "yourUser";
String password = "yourPassword";

Connection connection = DriverManager.getConnection(url, username, password);

Be sure to replace "yourDatabase", "yourUser", and "yourPassword" with the values specific to your environment.

Perform Database Operations

Use the connection to create and execute SQL statements. The "Statement" class is commonly used to execute simple queries, but for parameterized queries or to avoid SQL injection, consider using "PreparedStatement".

Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery("SELECT * FROM yourTable");

// process the result
while (resultSet.next()) {
     // read result data
}

// Close resources
resultSet.close();
statement.close();

Close the Connection

Always close the connection when you no longer need it to free up resources and prevent connection leaks.

connection.close();

Here is a more complete example:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class ExampleJDBC {
     public static void main(String[] args) {
         try {
             // load the JDBC driver
             Class.forName("com.mysql.cj.jdbc.Driver");

             // establish the connection
             String url = "jdbc:mysql://localhost:3306/yourDatabase";
             String user = "yourUser";
             String password = "yourPassword";

             Connection connection = DriverManager.getConnection(url, username, password);

             // execute an SQL query
             Statement statement = connection.createStatement();
             ResultSet resultSet = statement.executeQuery("SELECT * FROM yourTable");

             // process the result
             while (resultSet.next()) {
                 // read result data
                 String name = resultSet.getString("name");
                 int age = resultSet.getInt("age");
                 System.out.println("Name: " + name + ", Age: " + age);
             }

             // close resources
             resultSet.close();
             statement.close();

             // close the connection
             connection.close();
         } catch (Exception e) {
             e.printStackTrace();
         }
     }
}

Be sure to replace "com.mysql.cj.jdbc.Driver" with your database's specific JDBC driver. This example uses MySQL as a generic example. For other databases such as Oracle, PostgreSQL, SQLite and others, you will need to use the corresponding JDBC drivers.